Field of the Invention
The present invention relate to a light emitting device and a method for manufacturing the same.
Description of the Related Art
In recent years, in place of conventional light bulbs, light emitting diodes (each hereinafter referred to as an “LED”) have been increasingly used in lighting apparatus for general illumination and the like because of less power consumption. Application fields of the light emitting diodes have been expanded (JP 2008-041290 A, JP 2008-282754 A, JP 2011-159970 A). Among these applications, to improve a light extraction efficiency of second optical systems in spotlights, projectors, and the like, LED is required to have high light quality and high power output with decreased unevenness of brightness and color in a light emission surface while having as small a light emission portion as possible.
One of methods for reducing such unevenness of light emission involves blending a filler into a sealing material for a light emitting element to promote light diffusion.
For example, a light emitting device is proposed in which a blue LED is combined with a YAG phosphor that is excited with light emitted from the blue LED to emit yellow fluorescence to obtain a white LED. In this light emitting device, the YAG phosphor is blended into a sealing material, such as resin, for sealing the blue LED mounted in a cup. Into the same sealing material, a diffusion agent is also blended, in addition to the phosphor, thereby more effectively dispersing the phosphor into the sealing resin.
In such a structure, however, unevenness of color sometimes occurs. Specifically, in view of the length of an optical path traveled by the light emitted from the LED element until it is extracted from a light emission surface of the light emitting device, there might be a difference in optical length between light emitted directly from above the LED element and light emitted from the side surface of the LED element and passing through the sealing material. As a result, as the optical path length becomes longer, the amount of components that excite the phosphors dispersed in the sealing resin is increased to cause the shift of color tones. Thus, in some cases, the color unevenness occurs between the part directly above the light emitting element and the surroundings of the light emitting element in the planar view of the light emission surface of the light emitting device.